Metal oxide particle having core-shell structure and method for producing same

A core-shell type metal oxide particle comprising:

• a core comprising a metal oxide particle having an average primary particle diameter of 3 to 100 nm;
• and a shell comprising metal oxide particles having an average primary particle diameter of 1 to 7 nm and covering a surface of the core, wherein the metal oxide particle in the core has an average primary particle diameter greater than the average primary particle diameter of the metal oxide particles of the shell,
• wherein when a component (a) is titanium dioxide and a component (b) is a metal oxide other than titanium oxide, the core comprises a particle comprising the component (a) or a combination of the components (a) and (b), and the shell comprises a particle comprising the component (b),
• wherein the shell does not completely cover the core, leaving the core exposed, and
• the following requirements A and B are satisfied:
• the requirement A:
• in a test of bringing the core-shell type metal oxide particle into contact with a compound having a P—OH bond, the core-shell type metal oxide particle is found, by NMR, to have a P—O—Ti bond formed, and
• the requirement B:
• the core-shell type metal oxide particle has a refractive index of 1.85 or more.